There's nothing like raging success to bring on a pack of competitors, and that's exactly what's now happening in the enterprise-collaboration arena.

Ever since the public launch of its team-communication software two years ago, Slack has taken enterprises by storm, propelled by its freemium business model and plenty of investor enthusiasm. Today, it claims 2.3 million daily active users, more than 675,000 paid seats and over US$64 million in annual recurring revenue.

Two new contenders entered the scene this week, both hoping to claim a piece of the pie for themselves. On Wednesday, it was SpotCues with what it calls the industry's first location-based contextual social network. On Thursday, Kore debuted a "bot-based" messaging platform.

Different approaches, same general goal: doing Slack one better.

"What Slack has done is make this market extremely visible," said Adam Preset, a principal research analyst with Gartner. "Competitors are calculating whether Slack will own that entire market and placing a bet that individuals, teams and enterprises might want something different."

SpotCues' bet is on technology that uses Wi-Fi or geofencing to create a social network at any location, allowing users to join the network in real-time, interact with mobile users near them and access location-specific apps. SpotCues is launching into large businesses first with a focus on connecting and engaging employees, but it also plans to expand into other organized communities.

"Enterprises have long desired a culture-building tool designed specifically for social collaboration using mobile phones," said Praveen Kanyadi, cofounder of the company.

Kore, on the other hand, has focused on "bots," or lightweight programs that connect with third-party apps and business systems via APIs. Essentially, the bots let users communicate with apps and business systems through the same interface they use to chat with coworkers. More than 100 prebuilt bots come included, offering integration with a variety of enterprise software. Kore and SAP are also collaborating on more.

Kore promises to marry team communications and business systems "in a simple, modern interface that people will love," said Raj Koneru, the company's CEO. In addition, Kore gives CIOs the "control and security they need," he added.

While much of the rhetoric today is about Slack because of its early emergence as a de facto leader, "the target is actually this issue around team communications," said T.J. Keitt, a senior analyst with Forrester.

It's a big issue for enterprises. The market for the broader category of unified communications is about $42 billion worldwide, Gartner's Preset said. "That's a huge market. The messaging piece of it is relatively modest, but even a modest portion is a good amount."

There's plenty of room for competition, said Vanessa Thompson, a research vice president with IDC.

Slack's good timing and PR helped it capture the "eyes and ears" of venture capitalists, but the company also showed there are new options for solving the "increasingly systemic business challenge" of connecting project-based workers, Thompson said.

Modes of collaboration are converging from workspaces, presence, messaging, groups, activity streams, voice and video, she said. "New products can have any number of these capabilities natively or be able to connect with other services to serve broader needs," Thompson added.

Frequently, companies will use more than one collaboration tool.

"There is some displacement taking place, but we will see organizations running a number of Slack-type applications in parallel to solve different and diverse requirements," Thompson said.

Whether Slack's dominance continues remains to be seen.

"There's always the risk that the mega vendors in this space -- Microsoft, Google and IBM -- will decide they want to create something like Slack and bundle it into their popular collaboration and productivity portfolios," said Forrester's Keitt.

To keep growing its business, Slack will have to evolve its platform, and that poses risks of its own, he added.

While the competitive landscape may shift as more competitors emerge, there's no doubt of the category's continuing importance.

"The message is the atomic unit of collaboration," Preset said. "Organizations focused on communication really want to get the messaging platform right."

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Katherine Noyes has been an ardent geek ever since she first conquered Pyramid of Doom on an ancient TRS-80. Today she covers enterprise software in all its forms, with an emphasis on cloud computing, big data, analytics and artificial intelligence.